TY - JOUR A1 - Kargl, F. A1 - Engelhardt, M. A1 - Yang, F. A1 - Weis, H. A1 - Schmakat, P. A1 - Schillinger, B. A1 - Griesche, Axel A1 - Meyer, A. T1 - In situ studies of mass transport in liquid alloys by means of neutron radiography JF - Journal of physics / Condensed matter N2 - When in situ techniques became available in recent years this led to a breakthrough in accurately determining diffusion coefficients for liquid alloys. Here we discuss how neutron radiography can be used to measure chemical diffusion in a ternary AlCuAg alloy. Neutron radiography hereby gives complementary information to x-ray radiography used for measuring chemical diffusion and to quasielastic neutron scattering used mainly for determining self-diffusion. A novel Al2O3 based furnace that enables one to study diffusion processes by means of neutron radiography is discussed. A chemical diffusion coefficient of Ag against Al around the eutectic composition Al68.6Cu13.8Ag17.6 at.% was obtained. It is demonstrated that the in situ technique of neutron radiography is a powerful means to study mass transport properties in situ in binary and ternary alloys that show poor x-ray contrast. KW - Neutron radiography KW - Diffusion KW - Liquid alloys KW - Shear cell PY - 2011 DO - https://doi.org/10.1088/0953-8984/23/25/254201 SN - 0953-8984 SN - 1361-648X VL - 23 IS - 25 SP - 254201-1 EP - 254201-8 PB - IOP Publ. Ltd. CY - Bristol AN - OPUS4-23854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Solórzano, E. A1 - Beyer, Katrin A1 - Kannengießer, Thomas T1 - The advantage of using in-situ methods for studying hydrogen mass transport: Neutron radiography vs. carrier gas hot extraction JF - International journal of hydrogen energy N2 - Neutron radiography (NR) is compared with the commonly used carrier gas hot extraction (CGHE) technique. We performed isothermal hydrogen effusion experiments at 623 K to study the mass transport kinetics. The investigated material was technical iron. The quantification of the hydrogen mass flow is done for NR by using concentration standards. The temporal hydrogen concentration evolution in the sample coincides well for both methods, i.e. NR and CGHE, and is in good agreement with literature. The advantages of the NR method are the non-destructive nature of measuring and the in-situ determination of hydrogen concentrations with high spatial and temporal resolution. Remaining hydrogen inside the sample can be identified directly by the NR method. KW - Hydrogen diffusion KW - In-situ KW - Neutron radiography KW - Carrier gas hot extraction KW - Imaging PY - 2013 DO - https://doi.org/10.1016/j.ijhydene.2013.08.145 SN - 0360-3199 VL - 38 IS - 34 SP - 14725 EP - 14729 PB - Elsevier CY - Oxford AN - OPUS4-29413 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Pfretzschner, Beate A1 - Taparli, Ugur Alp A1 - Kardjilov, N. T1 - Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW JF - Novel Approaches for Nondestructive Testing and Evaluation N2 - Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets on the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc welding (GTAW). The in situ visualization of austenitization upon welding and subsequent α’-martensite formation during cooling could be achieved with a temporal resolution of 2 s for monochromatic imaging using a single neutron wavelength and of 0.5 s for polychromatic imaging using the full spectrum of the beam (white beam). The spatial resolution achieved in the experiments was approximately 200 µm. The transmitted monochromatic neutron beam intensity at a wavelength of λ = 0.395 nm was significantly reduced during cooling below the martensitic start temperature M s since the emerging martensitic phase has a ~10% higher attenuation coefficient than the austenitic phase. Neutron imaging was significantly influenced by coherent neutron scattering caused by the thermal motion of the crystal lattice (Debye–Waller factor), resulting in a reduction in the neutron transmission by approx. 15% for monochromatic and by approx. 4% for polychromatic imaging. KW - Neutron radiography KW - Debye–Waller factor KW - Austenite-to-martensite transformation KW - Low transformation temperature (LTT) steel KW - Bragg-edge imaging KW - Gas tungsten arc welding (GTAW) PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-559077 DO - https://doi.org/10.3390/app112210886 VL - 11 IS - 22 PB - MDPI AN - OPUS4-55907 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel A1 - Pfretzschner, Beate A1 - Schaupp, Thomas A1 - Kannengießer, Thomas A1 - Kardjilov, N. ED - Somerday, B. P. ED - Sofronis, P. T1 - Measurement of hydrogen distributions in metals by neutron radiography and tomography T2 - Material Perfomance in Hydrogen Environments - Proceedings of the 2016 International Hydrogen Conference N2 - Neutron imaging has become a valuable tool for measuring hydrogen distributions qualitatively and quantitatively in metals. Hydrogen mass flow can be measured inside cm thick Steel samples with 10 s temporal resolution. Hydrogen accumulations around craclcs in embrittled iron samples can be visualized three-dimensionally. The gas pressure of hydrogen in crack cavities has been measured to be in the ränge of 5 MPa to 15 MPa. This quality of information allows new insights for the analysis of damage mechanisms on a micrometer scale, e.g., of hydrogen blistering. Further, this method is nondestructive and provides local information in situ and in three dimensions with a spatial resolution of 20 µm - 30 µm. T2 - International Hydrogen Conference 2016 CY - Jackson Lake Lodge, Wyoming, USA DA - 11.09.2017 KW - Hydrogen KW - Neutron imaging KW - Neutron radiography KW - Neutron tomography PY - 2017 SN - 978-0-7918-6138-7 DO - https://doi.org/10.1115/1.861387_ch46 SP - 416 EP - 422 AN - OPUS4-42505 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Pfretzschner, B. A1 - Taparli, Ugur Alp A1 - Kardjilov, N. T1 - Time-Resolved Neutron Bragg-Edge Imaging: A Case Study by Observing Martensitic Phase Formation in Low Temperature Transformation (LTT) Steel during GTAW JF - Applied Sciences N2 - Polychromatic and wavelength-selective neutron transmission radiography were applied during bead-on-plate welding on 5 mm thick sheets on the face side of martensitic low transformation temperature (LTT) steel plates using gas tungsten arc welding (GTAW). The in situ visualization of austenitization upon welding and subsequent α’-martensite formation during cooling could be achieved with a temporal resolution of 2 s for monochromatic imaging using a single neutron wavelength and of 0.5 s for polychromatic imaging using the full spectrum of the beam (white beam). The spatial resolution achieved in the experiments was approximately 200 µm. The transmitted monochromatic neutron beam intensity at a wavelength of λ = 0.395 nm was significantly reduced during cooling below the martensitic start temperature Ms since the emerging martensitic phase has a ~10% higher attenuation coefficient than the austenitic phase. Neutron imaging was significantly influenced by coherent neutron scattering caused by the thermal motion of the crystal lattice (Debye–Waller factor), resulting in a reduction in the neutron transmission by approx. 15% for monochromatic and by approx. 4% for polychromatic imaging. KW - Austenite-to-martensite transformation KW - Neutron radiography KW - Bragg-edge imaging KW - Gas tungsten arc welding (GTAW) KW - Debye–Waller factor KW - Low transformation temperature (LTT) steel PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-538016 DO - https://doi.org/10.3390/app112210886 VL - 11 IS - 22 SP - 10886 PB - MDPI CY - Basel AN - OPUS4-53801 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Griesche, Axel A1 - Große, M. A1 - Schillinger, B. ED - Fritzsche, H. ED - Huot, J. ED - Fruchart, D. T1 - Neutron imaging T2 - Neutron Scattering and Other Nuclear Techniques for Hydrogen in Materials N2 - Neutron imaging methods are appropriate to investigate hydrogen distributions in several metallic systems. The large total neutron cross section of hydrogen compared to those of elements or isotopes, respectively, in usual structural materials like steels or zirconium alloys allows the detection even of small amounts of hydrogen in such materials. The dependence of the total macroscopic neutron cross section of the sample or component on the hydrogen concentration can be determined experimentally by means of calibration specimens with known hydrogen concentrations. Such a calibration allows for a full quantitative determination of the local hydrogen concentration with a spatial resolution better than 20 μm. Because neutron radiography is fast and non-destructive, in situ investigations of time-dependent processes like hydrogen absorption and release or hydrogen bulk diffusion can be performed. This chapter gives an introduction into the main neutron imaging methods, radiography and tomography, and gives as examples results of neutron imaging investigations of hydrogen in different steels and in zirconium alloys,respectively. KW - Neutron imaging KW - Neutron radiography KW - Hydrogen PY - 2016 SN - 978-3-319-22792-4 SN - 978-3-319-22791-7 DO - https://doi.org/10.1007/978-3-319-22792-4_7 SN - 1868-0380 SN - 1868-0372 SP - Chapter 7, 193 EP - 225 PB - Springer Nature CY - Zurich, Switzerland AN - OPUS4-36365 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Griesche, Axel A1 - Dabah, Eitan A1 - Kannengießer, Thomas T1 - Neutron imaging of hydrogen in iron and steel JF - Canadian metallurgical quarterly N2 - Neutron radiography and tomography have been used for a time resolved in situ analysis and a 3D mapping of hydrogen diffusion in iron and steel. Samples were electrochemically charged with hydrogen and afterwards neutron transmission images were taken. Hydrogen diffusion coefficients in duplex stainless steel were determined at 623 K by measuring and comparing the sample's mean intensity with a hydrogen-free reference sample and subsequent normalisation to standards with known hydrogen content. In technical iron and in supermartensitic stainless steel the hydrogen distributions have been investigated. The radiographic images in iron show blisters, cracks and the distribution of molecular hydrogen inside cracks. The analysis of the diffusion behaviour of hydrogen out of a blister illustrates the capabilities of the method with respect to time and spatial resolution. The neutron tomography of supermartensitic tensile stressed samples illustrates the capability to visualise hydrogen distributions three-dimensionally. ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- On a utilisé la radiographie neutronique et la tomographie pour une analyse in situ à résolution temporelle et une cartographie 3D de la diffusion de l'hydrogène dans le fer et l'acier. On a chargé des échantillons par électrochimie avec de l'hydrogène et ensuite on a pris des images par émission de neutrons. On a déterminé les coefficients de diffusion de l’hydrogène dans l'acier inoxydable duplex à 623 K en mesurant et en comparant l'intensité moyenne de l'échantillon avec un échantillon de référence sans hydrogène et une normalisation subséquente à des échantillons références à teneur connue en hydrogène. On a examiné la distribution d'hydrogène dans le fer technique et dans l'acier inoxydable supermartensitique. Les images radiographiques du fer montrent des soufflures, des fissures, et la distribution de l'hydrogène moléculaire à l'intérieur des fissures. L'analyse du comportement de diffusion de l'hydrogène hors d'une soufflure illustre les possibilités de la méthode par rapport à la résolution temporelle et spatiale. La tomographie neutronique des échantillons supermartensitiques chargés en traction illustre la capacité de visualiser les distributions d'hydrogène en trois dimensions. KW - Neutron radiography KW - Hydrogen KW - Diffusion KW - Iron KW - Steel KW - Blister KW - Hydrogen assisted cracking PY - 2015 DO - https://doi.org/10.1179/1879139514Y.0000000162 SN - 0008-4433 VL - 54 IS - 1 SP - 38 EP - 42 PB - Canadian Institute of Mining and Metallurgy CY - Montreal AN - OPUS4-32809 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel A1 - Dabah, Eitan A1 - Hilger, A. A1 - Kardjilov, N. A1 - Manke, I. A1 - Kannengießer, Thomas T1 - Neutron imaging of hydrogen in steels T2 - Materials Science & Technology (MS&T) 2013 (Proceedings) T2 - Materials Science & Technology (MS&T) 2013 CY - Montreal, Quebec, Canada DA - 2013-10-27 KW - Neutron radiography KW - Hydrogen KW - Diffusion KW - Steel PY - 2013 SP - 945 EP - 950 PB - Curran CY - Red Hook, NY AN - OPUS4-29506 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Griesche, Axel A1 - Beyer, Katrin A1 - Kannengießer, Thomas A1 - Calzada, E. T1 - Hydrogen diffusion measurements in steels using neutron imaging T2 - Annual Report 2011 of the scientific cooperation at Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) N2 - Revealing hydrogen embrittlement mechanisms in steels is of great interest to scientists and engineers. Neutron radiography makes it possible to measure in-situ hydrogen diffusion with high spatial and temporal resolution at concentrations as low as 20 ppm. We compare hydrogen-charged specimens with hydrogen-free reference specimens and use calibration standards to normalize the hydrogen concentrations. This allows quantitative tracking of the hydrogen concentration evolution as a function of time, space and temperature. Furthermore, a view into the material with 'neutron eyes' facilitates the detection of cavities that contain molecular hydrogen. KW - Hydrogen KW - Diffusion KW - Steel KW - Neutron radiography PY - 2012 UR - http://cdn.frm2.tum.de/fileadmin/stuff/information/documents/annualReports/Annual_Report_2011_online_version.pdf SP - 50 EP - 51 AN - OPUS4-25981 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Griesche, Axel A1 - Dabah, Eitan A1 - Pfretzschner, Beate A1 - Schaupp, Thomas A1 - Kannengießer, Thomas A1 - Schulz, M. A1 - Kardjilov, N. T1 - Measurement of hydrogen distributions in metals by neutron radiography and tomography N2 - In recent years, the optimization of the imaging stations at research reactors and especially the further development of the neutron detectors allowed the measurement of hydrogen distributions with increasing spatial and temporal resolution at lower detection limits at the same time. Hydrogen has compared to iron a high total neutron cross section, which allows with basic radiographic methods the visualization of hydrogen in two and three dimensions inside the microstructure of components. This enables the in situ measuring of hydrogen mass flows inside cm thick steel samples with a temporal resolution of 20 s as well as the quantitative measurement of hydrogen accumulations at the crack’s inner surfaces in hydrogen embrittled iron samples. For the first time, we detected directly gaseous hydrogen in the crack cavities and we could measure the gas pressure. This new quality of the information on a micrometer scale allows new insights for the analysis of damage mechanisms, e.g. of hydrogen embrittlement. Further, this method is non-destructive and provides local information in situ and in three dimensions with a spatial resolution of 20-30 µm, which is not accessible with common methods as e.g. thermal desorption spectroscopy. In this contribution, we show examples that demonstrate the spatial and temporal resolution of the neutron radiography and tomography method in order to visualize and quantify hydrogen accumulations at cracks. The measurements were performed at the research reactor BER II of HZB in Berlin and at the FRM II reactor of the neutron source Heinz Maier-Leibnitz in Garching. T2 - 2016 International Hydrogen Conference CY - Moran, Wyoming, USA DA - 11.09.2016 KW - Neutron imaging KW - Hydrogen embrittlement KW - Neutron tomography KW - Neutron radiography PY - 2016 AN - OPUS4-37700 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -